However well a metalled reed may be made in the first instance, its weservation in a good state depends greatly on prompt and judicious spuds. The mud that forms on the surface in wet weather should be eraped off and formed into heaps at the side (avoiding the side :hannels), until it is sufficiently dry for carting away; because, if left hu the surface, it would, while moist, soften the road and cause it to weak up, and after drying impede the running off of water from a affisequent shower. This operation has been usually performed by rand, but scraping-machines, patented by Messrs. Bourne and Harris, tam been introduced with partial success, and have been said to diminish the labour fully one-half. The winter season, from October o April, is considered the beat time for the addition of fresh mate 7ials, which are laid on in thin coats, and should always be applied as won as any hollow capable of retaining water is observed. For the purpose of keeping a supply of broken stone always at hand, depots for holding about twenty-four cubio yards of metal arc formed by the road-side, at intervals of a quarter of a mile or less, from which the stone is taken to the required spot in barrows. When laid on the road, according to Parnell, it is not necessary to pick up the old surface, as the now metal keeps the part under it wet and soft, and soon works in. MeAdem, however, recommended breaking up the surface of the road in every case where fresh stone is added.
Stone and lens Tramtray8.—T6ough an improvement on ordinary pavement, this description of road may be considered as a link be tween metalled and paved roads, stone tracks having been occasionally applied to common roads, and with great benefit. Stone tramways consist of wheel-tracks formed of large blocks of stone, usually granite, the surface of which is made so smooth as to offer very little resist ance to the rolling of the wheels, while the space between the tracks, being composed of broken stone, gravel, or rough pavement, affords secure footing for the horses. Iron tramways, in which cast or wrought iron plates are used instead of blocks of stone, have hitherto been very little used on ordinary roads, though their superior smoothness gives them a decided advantage, while their expense does not, as stated by Macneill, at all exceed that of granite. Iron tracks are sometimes made with a flat surface, but a slight concavity, as in Woodhouse's rail, which tends to keep the carriages more accurately in the right course, and is therefore an advantage when the vehicles used on the tramway are nearly uniform in width. The granite blocks used for stone tram ways are generally from 3 to 6 feet long, 12 to 18 inches wide, and 8 to 12 inches deep. Great care is necessary in bedding such large blocks ; and the joints require nice adjustment. They are frequently laid end to cud without any fitting into each other, but it has been proposed to dovetail the ends together, to insert a small stone as a dowel between two blocks, to use iron clamps, or to join the stones with oak tree nails. The granite tracks used on some steep ascents in the Holyhead mad are bedded on a pavement S inches thick, packed and grouted, and n layer of 3 inches of broken stones not exceeding 11f inch in diameter; a thin stratum of gravel, well rolled, being placed last of all to receive the blocks. When they are laid, the centre and side spaces are filled up with ordinary road material to the level of the tracks ; a row of common granite paving-stones, about 6 inches deep, 5 wide, and 9 long, being laid along each side of the tracks to prevent loose materials working on to them. Mr. Stevenson, in the ' Edinburgh Encyclopaedia,' recommends the use of smaller stones, as being cheaper and less liable to injury from vibration than those of the usual size. The dimensions recommended by him are 14 inches deep, 18 inches wide at the base, 12 inches wide at the top, and 0 to 9 inches long. The increased accuracy required in the numerous joints might pro bably counterbalance any advantage gained by the adoption of small stowes.
The great saving of power effected by the use of tramways for ordinary carriages is shown by numerous experiments, some of which, tried on the granite tracks of the Commercial Road in London, proved that a well-made waggon will run with increasing velocity, by the force of gravity alone, down a mean slope of 1 in 155. On this road a loaded waggon weighing tell tons was drawn with apparent ease by a single horse, up an ascent of 1 in 274, for a distance of about two miles. On an iron tramway laid in 1816 by the Forth and Clyde canal
company at Port Dundas, near Glasgow, a horse has taken n load of three tons on a cart weighing nine cwt., up an acclivity of 1 in 15, without difficulty, though he could not proceed with it on a common causeway with an easy line of draught ; and the carters agree that the horses take up three tons upon the iron tracks as easily as they did twenty-four on the common causeway previously ueed.
In order to ascertain the comparative durability of different kinds of stone for tramways, and for paving generally, Mr. Walker tried some experiments on blocks laid in a toll gateway on the Commercial Road tramway, the results of which were as follows i—The blocks were 18 'inches wide and 12 deep, and were laid down in March, 1830; and the loss given in the table was ascertained after they had been in use seventeen months, in August, 1831 :— Stone tramways have been adopted in many street pavements where a great traffic is carried on, particularly in some of the narrow streets in the city of London, with much advantage ; but their application to acclivities on ordinary roads has hitherto been more limited than their merits deserve. By their judicious introduction on a few steep incli nations, many hilly roads might, at a email expense, be made nearly equal to level lines ; and it is probable that such a measure would tend, in an important degree, to enable to meet the for midable rivalry of railways, In his report to the Holyhead-road Commissioners in 1839, Mr. Macneill strongly recommends the applica tion of stone or iron tracks to several hills, and states that an iron tramway laid down along the whole length of the road would reduce the expense of horse labour fully one half. a If," he writes, " a tramway were constructed of iron plates, the whole way from London to Bir mingham, a conch carrying sixteen passengers might be drawn at the rate of ten miles an hour with only two horses, and one horse would be able to draw a post-chain more easily than two now can, so that the expense of travelling might be reduced one half, and a similar reduction might be made in the charges for carrying goods. The expense of forming such a railway would be about 25001. a mile, making the whole expense from London to Birmingham 271,0001." In addition to the immediate advantages of such an improvement, it would remove one of the greatest obstacles to the successful use of steam locomotives on common roads Paresiests.—The formation of paved roads on correct principles appears to have been welPunderstood by the Romans, whose pavements show great care in their essential features,—a good foundation and accurate fitting of the stones. Some of the modern imitations of the Roman si the street-pavements of Italy show the like attention to these important points!, the paving-stones being set in mortar on a concrete foundatiou with a degree of accuracy that has led some writers to designate these roads liori--orstal mills. In some instances the blocks of stone used are of considerable depth ; but they are often thin, and, being of large dimensions, have more the character of fiag-etones than of ordinary paving At Naples and Florence, stones 2 feet square and 0 inches thick, laid diagonally across the road, and neatly set iu Poazuolano mortar, are used; the surfaces being chipped where declivities or turnings occur, to prevent the slipping of horses, which become very sure-footed from habit. Occasionally, as at Milan, kinds of paying are laid for the wheel-tracks and horse. lath, so as to produce the effect of a stone tramway. These pave ments have been recommended sa models for imitation in paving the streets of London ; but the durability with which they are oonstructed would form a disadvantage in a place where the pavement has to be frequently disturbed for the purpose of laying down or repairing water and gas-pipes, or cleansing the sewers' ; and it is probable that pave ments which answer well for the light vehicles and limited traffic of many of the continental cities, would be found quite Inadequate to bear the number of heavy carriages traversing the principal thorough fares of the metropolis ; of which some idea may be formes' from the fact that from six o'clock, A.11., of March 16, to six o'clock, ass., March 17, 1859, there were observed to pan over London Bridge, 41-83 cabs, 4230 omnibuses; 9215 waggons and carts, and 2130 other vehicles, or 20,444 in all.